#include<bits/stdc++.h>
using namespace std;
int ss(int a)
{
	int temp;
	for (int i=2;i<sqrt(a);i++)
	{
		if (a%i==0) return 0;
	}
	return 1;
}
int main()
{
	int a;
	cin>>a;
	if (ss(a)) cout<<"yes"<<endl;
	else cout<<"no"<<endl;
	return 0;
}